You are trying to remove a directory. When you run a "sudo rm -rf" command you get this error:
rm: cannot remove '/path/to/': Device or resource busy
When you run a "sudo umount /path/to/" command you get this error:
"umount.nfs: device is busy"
What should you do to eliminate the directory?
1. Is the "/path/to/" in the "sudo umount" command identical to the path in the error message? If so, skip to step #2. If not, remember that if you get an error like this "'/path/to/subdirectoryname': Device or resource busy", then you need to try the umount command *with* the subdirectory. The root cause of this is you are trying to umount a parent directory of a subdirectory that is mounted.
2. If the directory is not unmounting and you are using the "sudo umount" command, run these two commands:
sudo umount -f -l /path/to
# The -f flag is for force. The -l flag will clean up references to the file system. Using these two flags at the same time is recommended by various Linux experts when a directory will not unmount as it normally should.
sudo rm -rf /path/to